Refining of lead bullion containing other metals



G. K. WILLIAMS REFINING oF LEAD BULLION CONTAINING OTHER METALS Oct. 9,1928.

Filed Feb. 9, 1927 TIE Patented Oct. 9, 1928.

UNITED STATES GEORG .KENNETH WILLIAMS, 0F PORT PIRIE, SOUTH AUSTRALIA,AUSTRALIA.

REFINING OF LEAD BULLION CONTAINING OTHER METALS.

Application led February 9, 1927, Serial No. 166,988. and in AustraliaMarch 6, 1926.

zinc (With or without lead) and which beingf present in the initialbullion, it is desired to remove, both for their own values and for the-purpose of providing'lead sufficiently free therefrom for commercialpurposes.

A Hoy-such alloys of zinc (with or without lead) and the said alloyingmetals.

Residual bullion-the bullion remaining after treatment which isrelatively .low in one or more of the alloying metals.

@rustesuch alloys of the alloying metals with zinc and lead (with orwithout lead) which are formed by the cooling of the bullion as distinctfrom the alloys which are formed as conjugate solutions.

In the refining of lead bullion by the wellknown Parkes process, it isthe practice to incorporate a certainamount of Zinc with the moltenbullion sufficient for the formation of certain alloys with zinc and thesaid metals desired to be removed. The bullion is then cooled, wherebythe alloys separate from the bullion, and as the temperatures obtainingduring such cooling are below the melting points of the above alloys soliberated such alloys separate in the form of crusts. Such crusts, owingto theirspecific gravity being lower than that of the liquid bullionriseto the surface and are then removed, leaving residual bullion relativelylow in such metals.

The crusts obtained by y the aforesaid Parkes process usually contain aconsiderable amount of entangled lead, the removal of which has beeneffected, either by subjecting the said crusts to liquation, or topresses.

In the operation of the Parkes process, as universally practised, theamount of zinc added to the bullion and the temperatures employed areinsuicient for" the formation and maintenance of conjugate solutions ina liquid system enabling the separation of such solutions from eachother.

Now, the object of this present invention is to provide means wherebylead bullion containing the said alloyingmetals may yberelined for theremoval therefrom of the said alloying metals, providing on the one handalloys relatively rich in such alloying metals and low in lead, and onthe other hand residual bullion sufficiently low in such alloying metalsas required for commercial purposes, in amore economical and efficientmanner than heretofore.

According to this invention the refining of lead bullion may be effectedeither as a continuous or as an intermittent process, and the differentalloying metals imay be preferentially removed from the bullion givingalloys rich in one or more of the said alloying'metals in specificorder.

Now, I have found that if an amount of zinc beyond a certain quantitygreater than that which is used in the Parkes process is incorporatedwith bullion containing the said alloying metals,l and a Asuiiicientlyhigh temperature is maintained to liquefy the system layers of conjugatesolutions are formed, the top solution comprising the said alloy,V andthe bottom solution bullion, which, when cooled to about its eutectictemperature produces residual bullion. A

This invention therefore comprises cerv tain improvements in therefining of lead bullion containing alloying metals and -consists ofincorporating zinc with the said bullion in sufficient quantities andmaintaining the required temperature, whereby distinct molten layers ofconjugate solutions are formed, the upper of which consists of the saidalloy which may be separated, and the lower of which consists of bullionwhich, if desired, can be cooled to about its eutectic temperature,producing on the one hand residual bullion, and on the other hand alloysin the form of crusts relatively rich in zinc.

This invention-also comprises the preferential separation of the alloysof the alloying metals by the regulation of the amount of Zincincorporated with the bullion, and the temperature. to which the mixtureis submitted, whereby conjugate solutions are formed, the upper of whichcomprises an alloy rich in a certain alloying metal as distinct from theother alloying metals.

For example: Lead bullion containing copper, gold and silverpmay betreated in accordance with this invention by inco-r.L porating a.certain quantity of zinc withthe bullion and maintaining the saine atsuch a temperature that an alloy relatively rich in copper and gold andlow in silver, and a residual bullion relatively low in copper and goldand high in silver can be obtained. Or alternatively by incorporatinglarger amounts of zinc with the lead bullion an alloy relatively rich incopper and gold and silver an be obtained and a residual billion`relatively low in copper and gold and silver.

Consequently by this method oftreatment I am enabled to effect theremoval from the bullion of the copper and gold and silver in oneoperation, or by successive operations in which the quantities. of Zincpresent are co'ntrolled'to preferentially remove the copper and thegold, and thenthe silver. This preferential treatment is capable of manymodifications owing to the different aiinities possessed by zinc for thedifferent alloying metals. Zinc has a slirrhtly greater affinity forcopperthan for go d so that by lincorporating a relatively small amountof zinc with f the bullion and heating the saine to therequiredtemperature' alloys relatively higher in copper than in gold can beobtained, but for practical purposes'owing tothe fact that suchdifferences in the affinities of zinc for copper and gold are slight Iprefer toform alloys as relatively rich as possible lin both gold andcopper.I Inthe practical application of this invention regard should behad of the quantity of zinc present in the crusts formed during thecoolingof the bottom solution td about its eutecticl temperature, andthe zinc contents of such crusts are availed of to supply a proportionof the zinc required to be present in thevarious treatments carried outduring the refining operation, whereby economies are effected in theconsumption of zinc necessary for the carrying. out of the process.

Thus, in carr ing the invention Vinto practi' cal effect, it 1spreferred that a suitable amount of zinc beincorporated with the leadbullion and the vtemperature of the same f maintained at the required deree for the liquefaction of the alloy, where y conjugate solutions areformed, the lupper of which consists of the alloy which is separate-d,and the lower of which consists of bullion which when cooled to aboutits eutectic temperature gives residual bullion on the one hand andalloys in the form of crusts on the otheringI metal or metals.IlI-Iovvever, to obtain thel highest eiiciency with .respect to the lzinecon,- sumption and quantity ofcrusts formed during the cooling of thebottom solution, it is advisable that such bottom solution be cooled toabout its e'utectic temperature.

This improved method of refining lead bullion\,may be carried outxeitheras inter.

part of the treatment may be carried out in c a reverberatory -furnaceor a suitable container, and the other part in a suitable kettle.

One method of applying` the invention to refining `in ordinaryl openkettles, the requisite quantity of zinc (in the form of sp-clter with orwithout crusts obtained from the cooling of the bottom solution of thecorresponding treatment of the previous charge) is incorpo-rated withthe charge o'f bullion in the kettle (which may be either the leadbullion to be refined containing the said alloying metals, or residualbullion from a preceding preferential treatment) and the mixture isheated to the requisite temperature for the formation of conjugatesolutions, the top solution of which comprises the desired alloy, whichis separated, and the bottom solution is either cooled in the kettle orelse transferred to some other vessel of suitable-type l other suitablecontainer wherein the desired,

temperatures may be -maintained and molten .layers of conjugatesolutions formed. When operating in reverberatory furnaces precalitionshould be taken for avoiding oxidation of the bullion such as by areduclng atmos- ,phere in thesaid furnace or by forming a surface liquidlayer of a substance such as common salt.. Or such a reverberatoryfurnace may be used for preheating the bullion to the requiredtemperature before being fed into the separating kettle. Instead ofeffecting the incorporation of the zinc with the lead inthe kettleitself, such incorporation'may be effected in a separate vessel such asby causing the liquid bullion to pass through a bath or layer of moltenzinc previous to being fed to the kettle. Or instead of both' formingthe conjugate solutions and separating the4 same in the ione kettle orother suitable container the process may be A'applied using one kettleorvessel for in- Icorporation of the requisite quantity of zinc with thebullion and maintaining the required temperature lfor the formation ofconjugate solutions andthen discharging the same into a separate kettleo r suitable container when the bullion is cooled to the requisitetemperature for theseparation of the alloy comprising the conjugatesolution and also, if required, the crusts formed.

When such treatment is carried out in the ordinary open kettles whichare at present in use, the thickness of the surfa-ce layer of topconjugate solution comprising the alloy is relatively small, owing tothe large surface area, so that considerable diculty is experienced ineffecting al separation of the same Without undue contamination by, andentanglement of, the lower layer. of solution. Moreover, such openkettles as at present in use are adapted only for intermittent treatmentofl bullion in accordance with this invention.

Consequently ythe treatment of the said bullion in accordance with thisinvention is 1preferably effected in such manner that thel ture, andthis invention comprises the treati ment of the said lead bullion inavessel` oi kettle wherein the abovementioned conditions aie maintained.Kettles of this description are adapted for either intermittent -orcontinuous treatment of bullion.

A kettle of this description is illustrated in the accompanying drawingswherein Figure 1 is a view in sectional elevation; Figure 2 is a viewlin sectional plan of part of Figure 1 taken on the line 2 2; l'

Figure 3 is aiview in sectional plan of a part of Figure 1 taken on theline 3 3;

Figures 4 and 5 are vertical sections of portion of a ykettle showingthe accommodation of means foi` ensuring tlieadmixture of the metaltherein.

The kettle 10 consists of a deep narrow vessel having means suchas anupper circular flue 11`and a lower circular fiue 12 whereby thedifferent portions thereof may be differentially heated and a highertemperature imparted to the upper portion than to the lower.

`The kettle is provided with au upwardly projecting spout 13 from itslower portion` the/discharge 14 of whichis at a lower level than'the topof the kettle, and means may be provided, such as by a surrounding flue17 whereby the said spout may be also heated maintaining the same at therequired temperature. Y

As the upper portion of the kettle 10 is subjected to considerablyhigher temperatures than the lower portion the saine is more liable todeterioration and cracking, so thatl the kettle 10 is preferably formedintwo parts having tlangeslQ` and 20 by which the said parts may beboltedor otherwise fastened together, whereby the upperpart may berenewed Without having to dismantle the lower part. The joint betweenthe twoiflanges 19;

and 2O is made tight by forming a concentric groove 21 of circular crosssection therebetween, tlie same being adapted to accommodate a pipe 22through which a cooling medium (such as water) is caused to circulate,

thereby causing any metal entering the joint to freeze and leakagethereby avoided.

rllie upper flue 11- surrounding the u pper portion, of the kettle 10 isprovided with a liquid fuel bu-riier 15 or other source of heat wherebythe] same is'maintained at therequisite temperature.

The lower flueg12 surrounding the lower portion of the kettle 10 is alsoprovided with a liquid fuel burner 16or other source of heat wherebythesame is maintained at its requisite temperature. j i

In some cases it may be necessary to maintain the lower portion of thekettle 10 at a lowerl teiiipei'ature than would ensue by the mereabsence of heating means in the lower flue 12 and in such a case acooling medium (such as cool air) may be passed through the i said flue12. the same being for the time being cut off from the main combustionflue, orl if necessary-water circulating pipes may be disposed withinthe Said flue l2.

When adapting this invention for continu:

ous'treatment-the bullion is continuously fed into the'top of the kettlewith the requisite i amount of zinc Iand the' residual bullion islikewise continuously discharged from the.

bottom of the kettle, the alloy comprising thev i "upper layer ofconjugate solution being continuously or intermittently withdrawn.- In

'may be necessary,jthe alloys comprising the f upper layer of conjugatesolutions formed in each kettle being separately withdrawn eithercontinuously or intermittently.y .i

The following twofmethods of operating such treatment are mentioned byway of eX- ample. j

The bullion is continuously fed into the kettle-10 together with thedesired quantity of zinc, the upper part of the kettle 10 beingmaintained above the point of liquefaction ofv i jugate solution'bymeans of the burner 15 in the flue 11, whilst the lower part of thekettle 10 is maintained at a gradually decreasing temperature towardsthe bottom by regulating the temperature in the flue 12,- thetemthealloy comprising the upper layer of con` ,125.

perature at the entrance to the spout`13 being at approximately theeutectic temperature of the residual bullion.

The continuous feed of the lead bullion into the kettle 10 causes acontinuous formation of an upper layer of conjugate solution comprisingan valloy of one or more of the alloying metals anda continuousdischarge of residual bullion from the spout 13. In the passage of thebullion through the kettle vcruSts are formed in the lower portionsthereof due to cooling. These crusts rise into .the

'upper portion of the kettle, where they augment the aforesaid layer ofconjugate solution. If necessary, means may befprovided for ensuringthe' more or less complete admixture and if desired the same mayhcomprise a stirrer 23 fitted to a spindle`24 and disposed l alloyrequired, and thus the continuous feed ing, and by maintaining thedelivery of .residof bullion containing alloying metals and zinc intothe kettle 10 will cause the continuous formation of conjugatesolutions, the upper layer ofwhieh comprises an alloy rich in one ormore of the alloying metals.

Consequently the bullion is continuously subjected to treatment as itpasses through the kettle 10 whereby the particular alloying metal ormetals is or are separated therefrom so that when the said bullionreaches the lower portion of the kettle 10 which is maintained ,at aboutthe eutectic temperature of the residual bullion, it is relatively freefrom the said alloying metal or metals.

By maintaining the upward projecting spout 13 at a temperature abovewtheeutectic temperature of the residual. bullion, this residual bullion isprevented "from freezing as it flows upwardly through the said spout 13.whereby la continuous delivery may be effected, through the discharged14p so that by continuously or periodicallyremovin'g the upper layer ofalloy by either tapping or bailual bullion through the spout 13,- acontinuous feed may be maintained into the kettle 10 of the bullioncontaining the alloying metal.

As an illustration of the above modification of'thisinvent-ion I givethe following example of certain work performed by me at Port Pirie,South Australia: j

Example I A bullion assayng'zu Silver 57. 702s. per tcn Gold 1 grainCopper .r 0.004 per cent Zinc 0.2per cent y was continuously fed intothe top of a kettle similar to that illustrated in the accompanyingdrawings together with periodic additions of zinc (spelter) equivalentto 18-lbs per ton of bullion treated, the upper portion of the kettlewas maintained at a temperature of approximately 700 C. and the bottompartV of the kettle was cooled to a temperature of approximately 335 C.and the-spout at a temperature of approximately 400 C. A layer ofconjugate solution' was continuously formed in the upper part of thekettle and4 was periodically removed by hailing and was found to be15.7-lbs. per ton of bullion treated whilstl the residual bulliondischarged rfrom the spout of the kettle assayed-z 'Silver l0.2-ozs.perton Zinc 0.56 per cent Gold Trace Copper Trace l The kettleused in the above'experiment was 2-feet in diameter and 9-feet deep anda rate of feed .was 4maintained for a considerable period of ver100-tons per day, but'l it was found 4that a much greatenra'te of feedcould be maintained, the operation being limited by -the supplies ofbullion available and the'temporary nature of the plant. A y

The work done in the above mentioned experimentat Port Pirie was limitedby the nature of the material of which the kettle used was composed,viz: cast iron, but indications have been obtained that if the upperpart ofthe kettle were made of material which would withstand a temerature of from 800 C. to 850 C. so that al oys of a higher meltingpoint could be formed as conjugate solutions a differentialseparationcan be effected of the alloying metals copper and gold and silver andthe following is anexample of a method of treatment based upon the abovementioned indicationsz. l

4Enma/mph: [I: A bullion 'assaying:

of two kettles as shewn in Figure'l together with periodic additions ofzinc equivalent to 9-lbs. per` ton, the top portion of the kettle b eingmaintained at a temperature of about being fed continuously into thefirst of a series y 850 C. and the flower portion of ,the kettle i4cooled to a'temperature of approximately 330 C. andthe spout maintainedat a temj perature of abouti400o'C. conjugate solution formed at the topof the kettle equivalent to 7.7-lbs.- per ton ofvbullion treated couldbe periodically removed assaying:

'whilst the residual bullion assayed:

Silver 57. 7 ozs. per ton Gold V1 vgrain Copper O. 004 per cent Zinc0.2. per cent could be continuously fed into Hthe second kettlegivingthe same result as the above mentioned example. Y

According to another modification of this invention the zinc necessaryfor the formation of the conjugate solution may be fed yinto the kettleat the commencement of the operation so that a layer of zinc orconjugate solution high' in zinc is disposed in the upper part of thekettle through which the bullion is caused to continuously pass untilthe layer of conjugate solution becomes enriched to a sufficient extentwith the alloying metals desired to be removed. By this method oftreatment the bullion is fed in continuously and the residual bullionremoved continuously and the alloy removedperiodically. If desired anamount of zinc as isrequired to make up for that with-4 drawn intheresidual bullion may be added to the feed of bullion. This methodofoperation `dispenses with carefulfcalculation as to the amount of zinclfed with the bullion.

As anillustrationof this modification of the' invention the rkettle 10`is first charged with bullion up to the level of the discharge 14 of thespout 1.3, and zinc, or alloy relatively high in zinc, is thenadded'thereto tothe upper level of the top of the kettle. g Bullion(either the lead bullion to be refined containing the said alloyingmetals, or residual bullion-from a preceding treatment) is then fedcontinuouslyinto the saidkettle 10, being caused to pass down throughthe surface layer of molten zinc or alloy, in such a way that it isbrought in'to intimate contact with the same, and if necessary, for thispurpose suitable trays or baffles or stirrers may be-provided forensuring the more or less complete contact. Y*

The temperature around the upper part of the kettle 10 is maintained atthe necessary degree for the ,liquefaction of the alloy by means of theburne-rs'l in the flue 11, whilst the lower part bf the kettle ismaintained at a decreasing temperature by means of the lower flue 12until the bottom thereof is at about'the eutectic temperature of theresidual bullion. The spout 413 of the said kettle is also maintained ata temperature slightly above the said euteetic temperature by means ofthe iue 17, so that the said residual bullion is prevented fromfreezing, and is permitted of a continuous flow through the said spout13.

'Ihecrusts which are formed by the cooling in the lower part of thekettle rise into the upper portion of the kettle, Where they come incontact. with the bullion feeding into the kettle and the conjugatesolutions which exist in that portion of the kettle, the upper layer ofwhich is relatively high in zinc. rl'he conm tinuousfeed ofv bullioninto the kettle causes the gradual enrichment ofthe upper layer of 1 theconjugate solutions in alloying metals by incorporation of the sametherein.' At the same time intermittent -additions of zinc (spelter) maybe madein order to maintain the level of the solutions to compensate forthe zincwithdrawn in the residual bullion. v The flow of bullion intothe kettleis maintained until the content'of alloying metal or metals inthe residual bullion vrisesvbeyond a certain. determining limit. Whenthis limit is reached the upper layer of conjugate solution comprisingthe alloy rich in the said alloying metal or metals is removed bytapping or bailing and a further requisite quantity of zinc (spelter) oralloy rich in zinc is added.

By operating in this way no accurate determination of the amount of zinc(spelter) to be added is necessary, the continuous flow of the bullionfunctioning to increasingly enrich theI conjugate solutions formed untilthe desired i degree of enrichment is attained. Whilst the layer ofconjugate solution in the upper portion of the kettle is of high zinccontent and low in yalloying metals the residual bullion dischargingfrom the lower portion of the kettle is correspondingly low in the saidalloy-` ing metals and as the percentage of thesaid alloying metals inthe said upper layer of'conjugate solution increases there is acorresponding increase in the percentage of alloying metals in theresidual bullion. Consequently the content of the alloying metals in theresidual bullion discharged affords alrelatively accuratedeterminingpoint at which the alloy' should be removed and a freshcharge of zinc fed into the kettle. l By way of an illustration df thismodifica.- tionA of anapplicationof this invention the following isgiven by way of/example;

Example [Il: The ,bullion treated assayed as follows: f' f A kettlesimilar to that illustrated in the alccompanying-drawings 2-feet indiameter and 9-feet deep-*was charged with bullion up to the level ofthe discharge of thespout and 1600-lbs'. of zinc v(spelt-er) 'was fed onto the Vformation of conjugate solutions.

Silver 0. 05 ozs. per ton Zinc 0. 6- per cent The bullion wascontinuously fed in to the top of the kettle together with periodicadditions of zinc equivalent to 8.5-lbs. per ton, and this feed wascontinuously maintained until the silver content of the residual bulliondischarging from the spoilt had increasedl to 0.2-oz. per ton. Theoperation was stopped and it was found that approximately 200 tons ofbullion had been passed through the kettle.`

The alloy comprising the conjugate solution in the upper portion of thekettle Was hailed off and found to be 2680-lbs. equivalent toy 13A-lbs.per ton ofbullion treated, assaying:

Grold i 7-dwts.perton Y Silver 29.4 per cent= 9604 ozs. per ton Copper0. 67 per cent Zinc 59. 3 per cent Lead 10. 0 per cent In the abovedescription of this invention reference has only been made to thealloying metals present as governing the amount of zinc and thetemperature required for the It will, however, be understood that otherfactors will govern these conditions, such as for example the presenceof other metals' such as Antimony, Arsenic and Bismuth which are usuallyregarded and designated as Impurities.

Consequently in determining thev amount of4 zinc added and thetemperature required for the purposes-of this invention regard will behad to the aforesaid impurities in the bullion.

The amount of zinc and the temperature required for the formation ofconjugate solutions comprising' the desired alloying metal or metals maybe determined by a simple test on a laboratory scale. For this purpose asmall miniature kettle may be used comprising a narrow deep kettlesimilar in shape tothat illustrated in the accompanying drawings havingalso a similar spout and likewise-means for differentially heating thebody of the said kettle and the said spout..

If such experimental work is required to be,4 carried out attemperatures-above that 'which :mamas casgtJ iron will withstand such akettle may be constructed of any suitable material such as refractoryvmaterial Ihe bullion lInay be heated in a separate vessel and a certaindefinite quantity of zinc added, such as an amount equivalent to say8-lbs. per ton.

, This mixture is thencontinuously fed into the kettle which ismaintained at a temperature of approximately 335 C. at the bottom,

and the spout at a temperature of about 400o C. and the upper portion ofthe kettle at such a temperature as is required to just maintain theconjugate solutions formed,

v that is to say, if there is any indication of crusts in the top 'ofthe kettle it may be assumed that the temperatureis too low. and shouldbe increased. The feedis continued and the kettle maintained atthesetemperatures until equilibrium is established as indicated byperiodic assays of the residual bullion discharged from the spout. Inthis Way indications may be obtained as to whetherl yor'not greater orlesserquantities of zinc are required and the experiment is continuedwith varying 'amounts of zinc until the correct amount of zine isdetermined as indicated by the condition of the residual bulliondischarged from the spout after equilibrium of the system is establishedfollowing each successive variation in the amount of Zinc added:

1. A process for the refining of lead 'bull l10n containing alloyingmetals consisting of incorporating zinc with the said bullion in suchquantity a'nd Isubjecting the same to such differential temperaturesthat `molten `layers of conjugate solutions lare formed'the upper layercomprising an .alloy rich in a certain alloying metal or metals andseparating such alloy in liquid system. w

2. A process for the refiningv of-lead bullion which consists offeedingthesaid bullion continuously through a suitable vessel together withrtherequisite quantity of zinc and subjecting the same to differentialtemperatures as it passes through the said vessel, the temperature atthe top being such as to cause 4the formation of conjugate solu- -tionscomprising an alloy relatively rich in one or more of the' alloyingmetals, the temperature at the bottom'being at or about the eutectictemperature of the residual bullion separating the said alloy andcontinuously discharging the said residual bullion.V

3. In the refining of lead bu`llioncontain-` 120 ing alloying etalsincorporating zinc with the said bullion in such quantities and main`taining such atemperature that molten layers loo icav

ofconjugate solutions are formed comprising i an upper layer of an alloy'rich in a certain alloying metal ormetals separating such alloy inliquid system, maintaining the remain-` ing bullion at progressivelydecreasing temperatures to` about the eutectic temperature v j residualbullion'in liquid system.

ofthe residual bullion and separating such 4. In the refining of leadbullion containing alloying metals the preferential separa- .tion ofsuch alloying metals by incorporating a suliicient amount of zinc in thesaid bullion and maintaining the same at such temperature thatconjugatesolutions are formed comprising an alloy rich in a certain alloyingmetal or metals separating such alloy, cooling the remaining bullion toa point above its eutectic temperature and reheating the same at such atemperature or temperatures that other conjugate solutions are formedcoIn-. 4prising an alloy or alloys -rich in the remaining alloying metalor metals, separating such alloy or alloys and removing the residualbullion.

5. In the refining of lead bullion containing alloying metalscontinuously feeding the A said bullion vin a molten condition through anumber of kettlesin series together with the requisite quantity of zincand mlintaining a higher temperature at the top portion of the saidkettles in the said series than at the bottom portion thereof wherebyconjugate solutions are formed in-'theupper portions of the ket-tlesrich in certain alloying metals,- removing the said alloys from theupper portions of the said kettles and maintaining `the temperaf ture ofthe 'lower portion of the last kettle at a point just above theeutecticv temperature of the residual bullion in each kettle andremoving the residual bullion from the last kettle` in the series. i 6.In the reiningof .lead bullion containing alloying metals continuouslyfeeding the said bullion in molten condition through a seriesof kettleslto ether with the requisite quantityof zinc an maintaining such atemperaturev at the vupper vportion of" the-first kettle that a moltenlayer of conjugate solution is formed comp-rising an alloy'rich injugate solutions are Aformed comprisingl alyloys relatively high inother alloying metal Aor metals, :cooling the bullion in sthe' low-erortion of the second kettle to a temperature just abovethe eutectictemperature of the residual bullionl periodically or continuouslyseparating'th'e'alloy formed in theupper portion of the second kettleand continuously reing alloying metals continuously feeding the saidbullion in molten condition through a layer of molten zinc in the upperportion of a suitable kettle, maintaining the said upper portion of thesaid kettle at such a temperature that molten layers of conjugatesolutions are formed comprising an alloy of a certain alloying metal ormetals maintaining t-he lower portion of the said kettle ata temperaturejust above he eutectic temperatureof the residual bu lion therein,continuously discharging the residual bullion from the bottom of thesaid kettle until its contents in the alloying metal which is associatedwith the alloy in the aforesaid conjugate solution rea/ches apredetermineddimit, removing the said conjugate solution eomprising thesaid alloy relatively rich in such alloying metal and adding a furtherquantity of zinc to' form a further layer of molten zinc in the upperportion of the kettle and repeating the ing at such a relativelyihightemperature that molten layers of conjugate solutions are formed andmaintainin the lower portion of l the said column at a re atively lowtemperature just,above the eutectic temperature of the residual bullion,continuously removing Nthe said bullion and removing the alloy com.-

prising thesa-id conjugate solution.

9. In the reliningof lead bulllon containing gold, silver and copper,,incorporating zinc with the said bullionin such quantities andmaintaining the same at such a temperature -that molten layers ofconjugate solutions are'formed, the upper of which comprises an alloyrelativelyrich in copper` and gold and low in silver, separating thesaid-A alloy, maintainin the temperature ofthe remaining bullion justabove the eutectic temperature of the residual bullion relatively low 1ncopperand gold and high in silver, subsequently treating the saidresidual bullion with the requisite quantity vof zinc and maintainingthe same at such a temperature that conjugate solutions are formedcomprising an alloy relatively rich insilver and low in copper. andgold, separating ysuch alloy and discharging the said residualbullionrelatively. .j

'low in copper, old and silver.

In witness/.w ereof I hereunto aix my signature.

erronea-3 KNNETHVWILLIAMS. l

